In space diversity radio systems, two spaced antennas are used to feed a common receiver as a means of reducing outages due to multipath fading. For narrow band systems, dispersion effects can be neglected, and the signal combiner designed to maximize the combined output signal. Since signal diversity combining reduces the fade probability, it was expected that this technique would also reduce overall system outage time. However, it was found during a test period of over five months that at one location the combined signal actually produced more errored seconds than an unprotected channel.